If you could take a time-lapse movie of a city block starting in the 1920s, the changes would be predictable: Trees would rise and fall. The cars would change from boxy black Model T’s to colorful models with tail fins to the indistinct cars of today. Toys would litter the sidewalk as families start up, then disappear as they move on, only to be replaced by a new young family. The houses would stand like statues, occasionally changing their costumes. They would be the constant on the block while everything around them moved.

But what of the lives inside?

It seems like we’ll never know. Family histories are written in broad strokes and short paragraphs, if they’re written at all. Who perished young, who was carried down the stairs at the age of 90. Who went off to war and never came back; who moved away and started a branch of the family in another state. Outside of these stories — which are often oral, half-remembered, and eventually forgotten — there’s no place for the quotidian details of life to be matched to a particular place.

Until Lyfmap.com. This new local website anchors memories to a specific spot on a map. Click on a location — your old house, your elementary school, the park where you got your first kiss — and add your recollections and photos.

According to the site, which went live this summer, “As your Lyfmap grows, you will rediscover former childhood friends and neighbors, reconnect with lost acquaintances, and share your fond memories with others who have enjoyed those places as well.”

Larry Bieza, the St. Paul man behind the site, said he got the idea from listening to his father’s tales of growing up in Chicago.

“As a little kid, you’re not paying a lot of attention. But when he passed away, I felt this loss of history,” he said. “People have history that is only specific to them, and it disappears.”

“Star Wars” was an influence, as well.

“Two days after it came out, I was still thinking of the Cantina scene, and how, as I watched that film, I wondered what happened with all these other characters. What are their lives about? What’s interesting about them?”

Everyone has a story, after all. Even aliens.

You could make the case that placing memories isn’t all that vital. Who cares if you click on a location and it says a mean old lady lived there for a while and then there was a young couple who drove a VW bus? It’s not up there with sequencing the genome.

But imagine going back to your childhood neighborhood — at least on a map — and seeing entries about the kids who triked up and down the street, the grown-ups you knew only as the moms and dads. (The woman two doors down was a principal? The quiet retired man at the end of the block was a former POW who spent his summers volunteering in South American villages?)

You’d not only learn what you couldn’t have known earlier, but you’d also have a snapshot of the place at a time in American culture.

It’s hard to say which is more compelling — marking your own history around the city, or finding out where your history intersected with others. You might have a particular attachment to Uptown, an old apartment on the Mall, where a certain portion of your single days played out, for better or worse. Then you find out it also was where someone’s mom once lived. She was in accounting at Powers Department Store before she got married, and suddenly it’s not just your place. Of course you knew it had tenants before and after, but the ones in the past are ghosts, and the ones who came afterward seem like trespassers. Still, when you put a name to it, a story, a history, one nondescript apartment building becomes what it is: a real-life novel in progress.

It’s no less your home because it was once someone else’s. That’s true of a block. A city.

When you open Lyfmap and see all the dots, you marvel at the number of stories each represents. It’ll never be complete. Not even close. But it’s a start.

Bieza says he wants to start a Lyfmap for every business in the area, so you can learn the history of commercial as well as residential buildings. As it is, the site holds promise.

“Right now you can post in the middle of a lake, you can upload pictures of your fishing trip,” he said. “Wherever someone has a memory, it can be saved.”

Just don’t lie about the length of the fish. History is depending on you.